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• Reservoir Drawdown Frequency and Guidelines for Water Conservation Triggers Number of times (or percent of years) during the 77-year streamflow record in which reservoir storage would have declined to 20% or less during the following 18 months. Water Remaining in University Lake and Cane Creek Reservoirs 100% 95% 90% 85% 80% 75% 70% 65% 60% 55% 50% 45% 40% 35% 30% 25% MG 3358 3190 3022 2854 2886 2519 2351 2183 2015 1847 1679 1511 1343 1175 1007 839 Jan o 0 0 0 0 0 0 0 0 0 0 3 8.0 mgd 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 0°k 4% Feb o 0 0 0 0 0 0 o a 3 a a 8.2 mgd 0% 0% 0 % 0% 0% 0% 0% 0 % 0 % 4°/ 5 % 5% Mar 0 0 0 0 0 0 0 0 3 3 5 6 6 8.0 mgd 0% 0% 0 % 0% 0% 0°k 0°k 0°k 4% 4 % 6% 8% 8% Apr o 0 0 0 0 o a a s 7 s 1z 1a ?_' 8.3 mgd 0% 0% 0% 0% 0% 0% 5% 5% 8% 9% 12% 16% 18 % 22% May 0 0 0 4 6 13 15 17 24 , . 25 -- ?_7 33F,' 9.2 mgd 0°h 0% 0 % 5% 8% 17% 19°k 22°l0 31,%:~ 32°/ - 35, a3~r=_ Jun 0 0 3 3 3 4 10 12 18- 23?- 29;.- °,~'1~:~' 9-8 mgd 0% 0°/s 4% 4% 4% 5% 13 % 16% 23% 27 38 % 4d I ~r; JUI 0 0 0 0 3 4 6 12 16 % 22 - 25~~ 3A :' 10.5 mgd 0°k 0% 0% 0% 4% 5°k 8% 16°k 21% 29 % - . 34°/ 44%a: AUg 0 0 1 1 3 3 5 7 9 17 25 31"~~ 10.6 mgd 0% 0% 1 % 1 % 4% 4°k 6% 9% 12% 2.2% i 32%_~ 40>6 Sep 0 0 0 0 1 1 3 3 6 8 18 2T °~' 10.3 mgd 0% 0% 0% 0% 1 % 1 % 4% 4% B % 10% 23_°~la _ X3,5', _'~_ OCt 0 0 0 0 0 0 1 1 3 3 5 15 ~~2 `:, 9.8 mgd 0% 0% 0% 0°k 0% 0% 1°h 1% 4% 4% 6% 19% '32°k i. NOV 0 0 0 0 0 0 0 0 1 1 3 3 7 ~~:- 1~~ 9.0 mgd 0% 0% 0% 0% 0°k 0°k 0% 0% 1°h 1% 4% 4% 9% 25%=" i ~eC 0 0 0 0 0 0 0 0 0 0 1 1 3 5 8.1 mgd 0°/a 0°h 0°k 0% 0% 0% 0% 0% 0% 0% 1% 1% 4% 6% NORM ADV ~1 #2 1<i3 EMRG Conservation Stages and _ - 0-1% 4$% 9-21% 224"/A°' Risk Levels 2002 Reservoir Levels = Highlighted Cells Each cell of the table contains an integer and a percentage, which represent the probability that reservoir levels will decline to 20 percent or less of full capacity during the following 18 months. These were calculated from spreadsheet model runs of 77+ years of daily streamflow data, updated through January 2003, and driven by monthly water demand and reservoir storage at the beginning of each month. Calculations were based on an average annual raw water demand of 9.15 mgd (which was OWASA's average day demand during CY 2001, after a 10 percent reduction for process water recycling) adjusted by observed monthly ratios, which are reflected in monthly demands shown in the first column of the table . Each row of the table corresponds to a month, and each column corresponds to reservoir storage at the beginning of that month. Storage is subdivided into increments of 5% and also expressed as million gallons (MG). Colors indicate the corresponding conservation and risk levels proposed for each condition. One cell in each row is highlighted in black, representing actual reservoir storage conditions at the beginning of that month during 2002. Rev 2/27/03 l5